Sensitivity Test with Different Schemes for the Moist Processes Parameterization in a Hydrostatic Mesoscale Model
中尺度数值模式中湿过程参数化的敏感性试验

Sensitivities to different schemes of the moist physics in a hydrostatic mesoscale model is studied by applying this model in cold front case (FRONTS87-IOP2),in which large area of moist static unstable stratification is present within the frontal zone. Two kinds of moist simulations, one (called FPS) with a subgrid convection scheme and the other (called NCS) without it, are conducted. The cold front showed quite different structures between FPS and NCS. In FPS, only a single strong cold frontal band is present; but in NCS, two strong cold frontal bands, one long one short, are present. Besides, NCS experienced the dramatic development of vertical velocity in the moist static unstable frontal zone, whereas such problem did not appear in FPS. Having compared with satellite images and the ground-based observations, we found that although the overdevelopment problem is better controlled in FPS than in NCS, NCS gives a more realistic cold frontal structure in which a mutiple banded structure is found. We think that the hydrostatic approximation in the model is mainly responsible for the overdevelopment problem in the moist static unstable frontal zone in NCS. The use of the subgrid convection scheme in FPS, at one hand, has the development of vertical velocity get controlled by reducing or even eliminating the moist static unstable stratification, but at another hand, may filter out some significant mesoscale frontal structure which would otherwise have develooped in the most static unstable cold frontal zone.